How can I test that the IP Redirect Plugin is working?

1) You could use a VPN to 'pretend' to be in a different country. For example, I use one called Astrill. You can connect to a little piece of software on your computer, and then use an IP address in a different country. I'm in Australia, so I'll often choose a US-based IP address to test what it would look like from a US IP address, and so-on. This is the more 'advanced' version.

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2) For a simpler version: You can just add your own country to the list into the settings. For example, since I'm in Australia, if I put "AU" into the text box in the settings under "Location Redirect", then I'll see the plugin get activated. You can do that during testing, then when ready to launch, just remove it if you don't want that country code in there.